As disclosed in the prior art, to manually mount an additional part/component on a printed circuit board which is already mounted thereon with existing electronic components, it is feasible to mount the additional part/component on the printed circuit board, provided that a plurality of positioning holes are already formed on the printed circuit board. In other words, the additional part/component can be assembled to the printed circuit board by one of the positioning holes thereon. For example, a heat sink (a part/component) can be mounted on a south/north bridge chip (an electronic component). However, electronic components are usually side by side when mounted on a printed circuit board, and positioning holes are usually formed between the electronic components mounted on the printed circuit board. Hence, during a mounting process, a part/component is likely to collide with the electronic components mounted on the printed circuit board and get damaged.
Referring to FIG. 1, for a heat sink 3 equipped with a plurality of push pins 5 to be assembled to a chip 2 mounted on a printed circuit board 1, the prior art discloses that the heat sink 3 is assembled on the printed circuit board 1 by means of the engagement between the push pins 5 of the heat sink 3 and a plurality of positioning holes 4 of the printed circuit board 1, respectively. However, during the aforesaid assembly process, the assembly worker often fails to perform accurate alignment of the push pins 5 with the positioning holes 4 required for the aforesaid precise assembly process, because the positioning holes 4 fall within the shadow of the heat sink 3. The odds are that inaccurate alignment of the push pins 5 with the positioning holes 4 can end up in collision between the heat sink 3 and electronic components 6 on the printed circuit board 1. Another likely consequence of the process of aligning the push pins 5 and the positioning holes 4 is that the assembly worker exerts an inappropriate force upon the printed circuit board 1 and, as a result, the printed circuit board 1 is compressed and damaged.
Therefore, the conventional assembly process inevitably compromises the conforming rate of the mounting of an external part/component on a printed circuit board, as the conventional assembly process does not ensure that the external part/component can be safely mounted on the printed circuit board without causing collision thereto. Furthermore, an inappropriate force applied to the printed circuit board during an assembly process or an assembly process performed inappropriately on the printed circuit board is likely to damage the electronic components or parts/components mounted on the printed circuit board.